Microsoft has just responded to Google's move regarding Exchange ActiveSync. Sadly, instead of addressing the very real problems consumers are about to face, Microsoft starts talking about switching to Outlook.com.

but that still makes them non-standard proprietary extensions that Google can change on a whim.

Non-standard, Yes. Proprietary, no.
Google don't "own" these extensions and there are no licenses, restrictions or fees associated with implementing them.
Besides, many things now considered "standard" started out as non-standard.